The present invention relates in general to sealing arrangements and more particularly to an improved enclosure moisture and dust seal assembly especially suited for application in personalized, hand-held radio apparatus which includes a molded plastic enclosure.
In portable radio equipment, as well as many other applications, seal arrangements are included to block out moisture and dust so as to protect the internal component parts thereof.
Probably the most prevelent is the use of a formed gasket which fits snuggly into a provided groove and which is compressed to a required degree by a continuous tongue included on a mating part, such as a cover or the like. However, it will be appreciated that the gasket structure is relatively expensive and particularly so since it is specifically designed to fit but one contour, and thus has but one practical application. Moreover, such gaskets are frequently spliced together by adhesive, as well as requiring still additional adhesive for affixing and retaining the gasket in place. Build up of adhesive of course effects undesirable tolerences. In addition, seal effectiveness of the gasket remains largely a function of how tight the apparatus fasteners are, which control the degree of compression of the gasket.
It must also be kept in mind that gaskets of any type wear out with time and accordingly require field replacement. Gaskets that are glued in place are difficult to replace for that reason alone.
One alternative to the use of gaskets of the foregoing type has been the standard O-ring. O-rings are elastic and thus are easy to set in place. Conventionally they are seated in a formed groove effected in the apparatus during its molding operation. The assembly process then is relatively simple because the O-ring has a uniform shape, a uniform cross-section, and may be fabricated of an impregnated lubricant compound. The O-ring is always less expensive than a specially designed gasket arrangement. Moreover, its effectiveness is not determined by fastener tightness. It might also be pointed out that it additionally minimizes the human factors involved in an otherwise relatively complicated assembly operation.
However, the O-ring is not always suited to every application. This is particularly so regarding small, hand-held personalized apparatus having a molded plastic housing. This is because the O-ring must be seated in formed groove. If the enclosure is relatively large there is little difficulty in providing for such groove in the molding operation of the housing. Below a certain size, however, it is in fact difficult, and in certain instances, impossible to mold in such grooves because of the tooling involved and other factors. One solution to the molding problem is simply to provide a flat surface with essentially right angle corners, instead of the formed groove and wherein the O-ring structure is glued firmly in place at such right angle corners. This is as undesirable, in terms of difficulty of field replacement, as the glued-in contoured gasket arrangement.